US20070274744A1 - Developing apparatus and image forming apparatus - Google Patents
Developing apparatus and image forming apparatus Download PDFInfo
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- US20070274744A1 US20070274744A1 US11/753,596 US75359607A US2007274744A1 US 20070274744 A1 US20070274744 A1 US 20070274744A1 US 75359607 A US75359607 A US 75359607A US 2007274744 A1 US2007274744 A1 US 2007274744A1
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- developer
- supplying belt
- bearing body
- voltage
- developing apparatus
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G15/00—Apparatus for electrographic processes using a charge pattern
- G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
- G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
- G03G15/0806—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer on a donor element, e.g. belt, roller
- G03G15/0808—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer on a donor element, e.g. belt, roller characterised by the developer supplying means, e.g. structure of developer supply roller
Definitions
- the present invention relates to a developing apparatus and an image forming apparatus that incorporates the developing apparatus.
- a printer performs electrophotographic processes including charging exposing, developing, transferring, cleaning and neutralizing. Through these processes, a toner image is formed on a photoconductive drum, and is transferred onto a medium such as paper. Subsequently, the toner image is fixed into a permanent image.
- An electrophotographic printer incorporates a developing unit that usually uses one-component toner.
- a toner supplying roller formed of sponge supplies the toner to a developing roller, which in turn supplies the toner to the photoconductive drum to develop an electrostatic latent image with the toner into a toner image.
- An object of the invention is to solve drawbacks of conventional image forming apparatuses.
- Another object of the invention is to provide a developing apparatus that prevents a reversal image of the electrostatic latent image from being left in the layer of toner on a developing roller, and an image forming apparatuses that incorporates such a developing apparatus.
- a developing apparatus includes a developer bearing body that supplies developer to an image bearing body.
- the developing apparatus includes a developer supplying belt and a voltage supply.
- the developer supplying belt supplies developer to the developer bearing body.
- the voltage supply causes a first voltage to be developed on a first point on the developer supplying belt and that causes a second voltage to be developed on a second point on the developer supplying belt.
- the developer supplying belt is in contact with or in proximity to the developer bearing body.
- the developing apparatus further includes a drive shaft and a driven shaft.
- the drive shaft is driven in rotation by an external drive source.
- the drive shaft causes the developer supplying belt to run.
- the driven shaft is rotated by the developer supplying belt when the developer supplying belt runs.
- the power supply applies voltages to the drive shaft and driven shaft to produce the first voltage and the second voltage, the voltage applied to the drive shaft being different from the voltage applied to the driven shaft.
- the first voltage creates an electric field through which the developer is supplied from the developer supplying belt to the developer bearing body.
- the second voltage creates an electric field by which the developer is recovered from the developer bearing body to the developer supplying belt.
- a developing apparatus includes a developer bearing body that supplies developer to an image forming body.
- the apparatus includes a drive shaft, a driven shaft, a developer supplying belt, an urging member, and a voltage supply.
- the drive shaft is driven in rotation by an external drive source.
- the developer supplying belt is entrained about the drive shaft and the driven shaft, the developer supplying belt supplying developer to the developer bearing body.
- the urging member maintains the developer supplying belt in tension.
- the voltage supply develops a potential difference across the drive shaft and the driven shaft.
- the developer supplying belt is in an abutting relation with the developer bearing body.
- the voltage supply creates the first voltage at a first point at which the developer supplying belt contacts the developer bearing body and the second voltage at a second point at which the developer supplying belt contacts the developer bearing body.
- the first voltage develops a first electric field across the developer supplying belt and the developer bearing body, the developer being supplied from the developer supplying belt to the developer bearing body through the first electric field.
- the second voltage develops a second electric field across the developer supplying belt and the developer bearing body, the developer being recovered from the developer bearing body to the developer supplying belt through the second electric field.
- the developer supplying belt is formed of a semi-conductive material having a volume resistivity in the range of 10 6 to 10 8 ⁇ cm.
- the developing apparatus further includes a rotating body that rotates in contact with the developer supplying belt.
- the developing apparatus further includes a rotating body that rotates in contact with the developer supplying belt.
- An image forming apparatus incorporates the aforementioned developing apparatus.
- a developing apparatus includes a developer bearing body, a first shaft, a second shaft, a developer supplying belt, and a power supply.
- the developer bearing body is in contact with an image forming body.
- the first shaft is driven in rotation by an external drive source.
- the developer supplying belt is entrained about the first shaft and second shaft, the developer supplying belt being partially in a wrapping contact with the developer bearing body.
- the power supply applies voltages to the first shaft and the second shaft such that a voltage drop appears in the developer supplying belt in a direction of travel of the developer supplying belt.
- the power supply applies a voltage to the developer bearing body such that a first electric field having a first direction is developed across the developer bearing body and a first portion of the developer supplying belt in contact with the developer bearing body, and such that a second electric field having a second direction opposite to the first direction is developed across the developer bearing body and a second portion of the developer supplying belt in contact with the developer bearing body.
- the first electric field allows the developer to be supplied from the developer supplying belt to the developer bearing body.
- the second electric field allows the developer to be recovered from the developer bearing body to the developer supplying belt.
- the developing apparatus further includes an urging member that urges the developer supplying belt to maintain the developer supplying belt in tension.
- the developer supplying belt is formed of a semi-conductive material having a volume resistivity in the range of 10 6 to 10 8 ⁇ cm.
- the developing apparatus further includes a rotating body that rotates in contact with the developer supplying belt at a portion after the developer has been recovered from the developer bearing body to the developer supplying belt.
- FIGS. 1A and 1B illustrate a general configuration of a developing unit of an image forming apparatus of a first embodiment
- FIG. 2 illustrates a general configuration of a print engine
- FIGS. 3 and 4 illustrate the voltages appearing on points P 1 and P 2 , respectively;
- FIG. 5 illustrates a pertinent portion of a printer of a second embodiment
- FIG. 6 illustrates the development process of a second embodiment.
- FIG. 1A illustrates a general configuration of a developing unit of an image forming apparatus.
- FIG. 2 illustrates a general configuration of a print engine.
- a photoconductive drum 11 includes an outer layer formed of an organic photoconductive material.
- a charging roller 12 uniformly charges the surface of the photoconductive drum 11 to approximately ⁇ 600 V.
- the charging roller 12 is in rolling contact with the photoconductive drum 11 , thereby minimizing wear of the surface of the photoconductive drum 11 due to friction.
- a negative direct current voltage is applied across the charging roller 12 and the photoconductive drum 11 .
- An LED print head 13 includes light emitting diodes (LEDs) as a light source, and illuminates the charged surface of the photoconductive drum 11 to form an electrostatic latent image.
- LEDs light emitting diodes
- a laser print head may be used in place of the LED print head.
- a developing unit 21 includes a developing roller 14 , a toner supplying belt 16 , a developing blade 20 , and a toner reservoir 17 .
- the developing roller 14 supplies toner 18 to the photoconductive drum 11 .
- the developing blade 20 forms a thin layer of toner 18 on the developing roller 14 .
- the toner reservoir 17 holds the fresh toner 18 therein.
- the developing roller 14 is in contact with or in proximity to the photoconductive drum 11 .
- the developing roller 14 rotates in a direction shown by arrow B, opposite to the direction shown by arrow A in which the photoconductive drum 11 rotates.
- the developing roller 14 supplies the toner 18 to the electrostatic latent image on the photoconductive drum 11 , thereby developing the electrostatic latent image into a toner image.
- the toner image is transferred onto paper 29 with the aid of a transfer roller 15 .
- the residual toner 18 remaining on the photoconductive drum 11 after transfer is removed by a cleaning blade 19 which serves as a cleaning device of the blade type.
- the paper 29 is then advanced to a fixing unit where the toner image is fused into the paper 29 .
- the developing roller 14 includes a metal shaft and a resilient layer formed on the metal shaft.
- the resilient layer is formed of a material such as silicone rubber or urethane rubber having a volume resistivity in the range of 10 8 to 10 10 ⁇ cm.
- a coating layer may be formed on the resilient layer.
- the developing roller 14 has a diameter of, for example, 20 mm.
- the developing blade 20 is formed of a thin metal plate having a bent end portion which is in pressure contact with the outer surface of the developing roller 14 .
- the toner supplying belt 16 is formed of a material such as semi-conductive urethane resin, polyimide resin, polyimideamide resin, urethane rubber, CR rubber, or silicone rubber.
- the toner supplying belt 16 has a volume resistivity in the range of 10 6 to 10 8 ⁇ cm, and a surface roughness Rz in the range of 5 to 15 ⁇ m.
- the toner supplying belt 16 is entrained about a drive shaft 16 a and a driven shaft 16 b , which are formed of a highly electrically conductive material such as metal.
- the drive shaft 16 a rotates, the toner supplying belt 16 runs.
- the driven shaft 16 b also rotates.
- the driven shaft 16 b is urged by coil springs 22 in a direction away from the drive shaft 16 a , so that the toner supplying belt 16 is maintained in a predetermined tension.
- the toner supplying belt 16 between the drive shaft 16 a and driven shaft 16 b partially wraps around the developing roller 14 such that the toner supplying belt 16 is in contact with the developing roller 14 over a circumferential distance L of the developing roller greater than a nip formed between the developing roller 14 and a conventional toner supplying roller of sponge.
- the conventional toner supplying roller having a diameter of 20 mm forms a nip of about 2 mm while the toner supplying belt 16 wraps around the developing roller 14 over a circumferential distance L of about 10 mm, from point P 1 to point P 2 .
- the toner 18 is one-component toner containing a resin such as polyester or polystyrene, a coloring agent, a releasing agent, and a charge control agent.
- An external additive such as silica is added to the surface of the toner.
- the toner is manufactured by pulverization or by polymerization.
- the toner 18 has a volume mean particle diameter in the range of 3-10 ⁇ m and an average degree of sphericity in the range of 0.9-0.98.
- the average degree of sphericity of the toner 18 is obtained by dividing the total number of degrees of sphericity of toner particles by the number of the toner particles (e.g., 3500). The average degree of sphericity is measured with a particle size and shape image analysis flow cytometer (MODEL FPIA-2000, available from Sysmex Corporation). Degree of sphericity is a measure of surface roughness of the toner 18 , and is given by the following equation.
- Degree of sphericity (total length of the perimeter of a projected area of a particle)/(total length of the perimeter of a projected image of a particle)
- the projected area of a particle is an area of the projection of a particle and is a binary image.
- the total length of the perimeter of a projected image of a particle is a sum of lengths between two adjacent edge points on the perimeter.
- the degree of sphericity of the particle is 1.00.
- the degree of sphericity of a toner particle becomes smaller with increasing complexity of its shape.
- the amount of charge of the toner 18 is measured by the charge blow-off method, and is in the range of ⁇ 60 to ⁇ 20 ⁇ Q/g depending on the charging agent and the external additive.
- a high voltage supply 81 applies a voltage VD to the developing roller 14 .
- a high voltage supply 82 applies a voltage VL to the developing blade 20 .
- a high voltage supply 83 applies a voltage VS to the drive shaft 16 a .
- a high voltage supply 84 applies a voltage VR to the driven shaft 16 b.
- a drive motor (not shown) rotates to drive the photoconductive drum 11 , developing roller 14 , and drive shaft 16 a in rotation in directions shown by arrows A, B, and D, respectively.
- the toner supplying belt 16 runs in the toner reservoir 17 with the toner 18 adhering to the toner supplying belt 17 .
- the toner 18 adheres to the toner supplying belt 16 by Van der Waals force and very small Coulomb forces resulting from the surface roughness of the toner supplying belt 16 .
- the toner 18 on the toner supplying belt 16 is brought into contact with the developing roller 14 at point P 1 .
- FIGS. 3 and 4 illustrate the voltages appearing on points P 1 and P 2 , respectively.
- Vp 1 ⁇ Db /( Da+Db ) ⁇ ( VS ⁇ VR ) (1)
- Vp 2 ⁇ Df /( De+Df ) ⁇ ( VS ⁇ VR ) (2)
- Vp 1 is a voltage at point P 1
- Vp 2 is a voltage at point P 2
- Da is the distance between point P 1 and the drive shaft 16 a
- Db is the distance between point P 1 and the driven shaft 16 b
- De is the distance between the point P 2 and the drive shaft 16 a
- Df is a distance between the point P 2 and the driven shaft 16 b.
- the voltage difference Vs ⁇ VR is apportioned by the resistances proportional to the distance Da and Db, resulting in voltage drops Vp 1 and Vp 2 at points P 1 and P 2 , respectively.
- the voltage at point P 1 is ⁇ 450 V from Equation (1).
- Vp 1 is ⁇ 450, which creates an electric field required for the negatively charged toner 18 (e.g., ⁇ 60 to ⁇ 20 ⁇ Q/g) to be transferred onto the developing roller 14 .
- the blade 20 forms a thin layer of toner 18 .
- the voltage VL is applied to the developing roller 20 for controlling the amount of charge and the thickness of the toner layer formed on the developing roller 14 .
- the thin layer of toner 18 is brought into contact with the electrostatic latent image formed on the photoconductive drum 11 , thereby developing the electrostatic latent image with the toner 18 into a toner image.
- a portion of the thin layer that is not brought into contact with the electrostatic latent image remains on the developing roller 14 , and reaches point P 2 as the developing roller 14 rotates further.
- the toner 18 deposited on the toner supplying belt 16 reaches point P 1 as the toner supplying belt 16 runs.
- the voltage Vp 1 at point P 1 at which the toner supplying belt 16 moves into contact with the developing roller 14 differs from the voltage at point P 2 at which the toner supplying belt 16 moves out of contact with the developing roller 14 .
- the voltage Vp 1 serves to establish an electric field through which the toner 18 is supplied from the toner supplying belt 16 to the developing roller 14 .
- the voltage Vp 2 serves to establish an electric field through which the remaining toner 18 is recovered from the developing roller 14 to the toner supplying belt 16 .
- the toner 18 remaining on the developing roller after the development of an electrostatic latent image may be removed from the developing roller 14 .
- the toner 18 recovered by the toner supplying belt 16 is then delivered to point P 1 , being re-used efficiently.
- a conventional toner supplying roller 16 is formed of sponge, the toner supplying roller 16 will deteriorate after a relatively short-time use, causing variations of supply of the toner 18 to the developing roller 14 even within a page of image, resulting in variations in the density of image.
- the pressure applied by the toner supplying belt 16 against the developing roller 14 may be controlled by adjusting the urging force of the coil springs 22 such that the toner supplying belt 16 exerts a relatively small abutting force on the developing roller 14 .
- a small abutting force not only prolongs the useful life of the toner supplying belt 16 but also minimizes the force that rubs the surface of the developing roller 14 , preventing the quality of toner 18 from being deteriorated as well as ensuring reliable image quality.
- the abutting force is preferably in the range of 5 to 20 g/cm for reliable abutment of the toner supplying belt 16 against the developing roller 14 .
- FIG. 1B illustrates a general configuration of a developing unit of an image forming apparatus where the toner supplying belt 16 is not in contact with the developing roller 14 but in proximity to the developing roller 14 .
- the high voltage supply 81 applies the voltage VD to the developing roller 14 .
- the high voltage supply 83 applies the voltage VS to the drive shaft 16 a .
- the high voltage supply 84 applies the voltage VR to the driven shaft 16 b .
- the voltage Vp 4 and the voltage Vp 5 appears at point P 4 and point P 5 , respectively.
- the voltage Vp 4 creates an electric field across the developing roller 14 and the toner supplying belt 16 in a direction such that the charged toner 18 may be transferred from the toner supplying belt 16 to the developing roller 14 .
- the voltage Vp 5 creates an electric field across the developing roller 14 and the toner supplying roller 16 in a direction such that the charged toner 18 may be transferred from the developing roller 14 to the toner supplying belt 16 .
- the configuration in FIG. 1B also provides the same advantages as that shown in FIG. 1A .
- FIG. 5 illustrates a pertinent portion of a printer of the second embodiment.
- FIG. 6 illustrates the development process of a second embodiment.
- a developing unit 24 includes a toner delivering roller 23 that rotates.
- the toner delivering roller 23 includes an electrically conductive shaft formed of a metal material.
- the electrically conductive shaft is covered with a semi-conductive rubber material or a foamed rubber material.
- the semi-conductive rubber material may be urethane or silicone and have a volume resistivity in the range of 10 6 -10 8 ⁇ cm.
- the foamed rubber material may be urethane or silicone and have a volume resistivity in the range of 10 6 -10 8 ⁇ cm.
- a drive motor (not shown) rotates to drive a photoconductive drum 11 , a developing roller 14 , toner delivering roller 23 , and a drive shaft 16 a in rotation in directions shown by arrows A, B, and D, respectively.
- the toner delivering roller 23 parallels to a developing roller 14 and is on the side of a toner supplying belt 16 opposite the toner developing roller 14 .
- the toner delivering roller 23 abuts the toner supplying belt 16 between a drive shaft 16 a and driven roller 16 b .
- the toner delivering roller 23 is driven by a drive motor (not shown) to rotate in a direction shown by arrow E, which is the same direction as the toner supplying belt 16 .
- the toner delivering roller 23 is in contact with the toner supplying belt 16 at point P 3 .
- the toner delivering roller 23 and the toner supplying belt 16 run in opposite directions at point P 3 .
- the toner delivering roller 23 is positioned relative to the toner supplying belt 16 such that the toner delivering roller 23 and the toner supplying belt 16 make no wrapped portion or little or no nip.
- a power supply 85 applies a voltage VP to the toner delivering roller 23 . While the photoconductive drum 11 , developing roller 14 , toner delivering roller 23 , and a drive shaft 16 a have been described as being driven by the same motor (not shown), the toner delivering roller 23 may be driven by a separate motor.
- Vp 3 ⁇ Dh /( Dg+Dh ) ⁇ ( VS ⁇ VR ) (3)
- Vp 3 is a voltage at point P 3
- Dg is the distance between point P 3 and the drive shaft 16 a
- Dh is the distance between point P 3 and the driven shaft 16 b.
- the voltage difference VS ⁇ VR is apportioned by the resistances proportional to the distance Dg and Dh, resulting in the voltage Vp 3 at point P 3 .
- the voltage Vp 3 is substantially equal to the voltage VP.
- Vp 3 is ⁇ 250 V.
- the drive motor Upon initiation of image formation, the drive motor is energized to drive the photoconductive drum 11 , developing roller 14 , drive shaft 16 a , and toner delivering roller 23 to rotate in directions shown by arrows A, B, D, and E.
- the toner delivering roller 23 rotates with the toner 18 adhering thereto while the toner supplying belt 16 runs with the toner 18 adhering thereto.
- the toner 18 adhering to the toner delivering roller 23 is brought into contact with the toner supplying belt 16 at point P 3 . Because the voltage Vp 3 at point P 3 is substantially equal to the voltage VP applied to the toner delivering roller 23 , no significant electric field is developed between toner supplying belt 16 and the toner delivering roller 23 . Therefore, the toner 18 is smoothly supplied from the toner delivering roller 23 to the toner supplying belt 16 . The resultant thickness of toner layer on the toner supplying belt 16 is substantially the same as that on the toner delivering roller 23 .
- a portion of the thin layer that is not brought into contact with the electrostatic latent image remains on the developing roller, and reaches point P 3 as the toner supplying belt 16 runs further. Because of negligible electric field between toner supplying belt 16 and the toner delivering roller 23 , the toner delivering roller 23 rubs the toner 18 on the toner supplying belt 16 to prevent the remaining toner 18 from forming a reverse image of the electrostatic latent image as a whole.
- the toner delivering roller 23 delivers the toner 18 to the toner supplying belt 16 continuously, a layer of the toner 18 may be formed on the toner supplying belt 16 . This ensures reliable supply of the toner 18 to the developing roller 14 .
- the toner 18 not used for the development of an electrostatic latent image is recovered by the toner supplying belt 16 , and the layer of the toner 18 is scraped off the toner supplying belt 16 by the toner delivering roller 23 .
- This provides reliable removal of the reversal image of the electrostatic latent image remaining in the layer of the toner 18 formed on the developing roller 14 .
- the present invention may be applicable to a copying machine, a facsimile machine, and a multi function apparatus of these machines.
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Abstract
Description
- 1. Field of the Invention
- The present invention relates to a developing apparatus and an image forming apparatus that incorporates the developing apparatus.
- 2. Description of the Related Art
- Among conventional image forming apparatuses based on electrophotography are printers, copying machines, facsimile machines, and other multi function apparatuses. A printer performs electrophotographic processes including charging exposing, developing, transferring, cleaning and neutralizing. Through these processes, a toner image is formed on a photoconductive drum, and is transferred onto a medium such as paper. Subsequently, the toner image is fixed into a permanent image.
- An electrophotographic printer incorporates a developing unit that usually uses one-component toner. A toner supplying roller formed of sponge supplies the toner to a developing roller, which in turn supplies the toner to the photoconductive drum to develop an electrostatic latent image with the toner into a toner image.
- During developing process, only the toner on the developer roller that is brought into contact with the electrostatic latent image is transferred to the photoconductive drum to develop the electrostatic latent image, and the rest remains on the photoconductive drum. This may leave a reversal image of the electrostatic latent image on the developing roller.
- An object of the invention is to solve drawbacks of conventional image forming apparatuses.
- Another object of the invention is to provide a developing apparatus that prevents a reversal image of the electrostatic latent image from being left in the layer of toner on a developing roller, and an image forming apparatuses that incorporates such a developing apparatus.
- A developing apparatus includes a developer bearing body that supplies developer to an image bearing body. The developing apparatus includes a developer supplying belt and a voltage supply. The developer supplying belt supplies developer to the developer bearing body. The voltage supply causes a first voltage to be developed on a first point on the developer supplying belt and that causes a second voltage to be developed on a second point on the developer supplying belt. The developer supplying belt is in contact with or in proximity to the developer bearing body.
- The developing apparatus further includes a drive shaft and a driven shaft. The drive shaft is driven in rotation by an external drive source. The drive shaft causes the developer supplying belt to run. The driven shaft is rotated by the developer supplying belt when the developer supplying belt runs. The power supply applies voltages to the drive shaft and driven shaft to produce the first voltage and the second voltage, the voltage applied to the drive shaft being different from the voltage applied to the driven shaft.
- The first voltage creates an electric field through which the developer is supplied from the developer supplying belt to the developer bearing body. The second voltage creates an electric field by which the developer is recovered from the developer bearing body to the developer supplying belt.
- A developing apparatus includes a developer bearing body that supplies developer to an image forming body. The apparatus includes a drive shaft, a driven shaft, a developer supplying belt, an urging member, and a voltage supply.
- The drive shaft is driven in rotation by an external drive source. The developer supplying belt is entrained about the drive shaft and the driven shaft, the developer supplying belt supplying developer to the developer bearing body. The urging member maintains the developer supplying belt in tension. The voltage supply develops a potential difference across the drive shaft and the driven shaft.
- The developer supplying belt is in an abutting relation with the developer bearing body.
- The voltage supply creates the first voltage at a first point at which the developer supplying belt contacts the developer bearing body and the second voltage at a second point at which the developer supplying belt contacts the developer bearing body.
- The first voltage develops a first electric field across the developer supplying belt and the developer bearing body, the developer being supplied from the developer supplying belt to the developer bearing body through the first electric field. The second voltage develops a second electric field across the developer supplying belt and the developer bearing body, the developer being recovered from the developer bearing body to the developer supplying belt through the second electric field.
- The developer supplying belt is formed of a semi-conductive material having a volume resistivity in the range of 106 to 108 Ωcm.
- The developing apparatus further includes a rotating body that rotates in contact with the developer supplying belt.
- The developing apparatus further includes a rotating body that rotates in contact with the developer supplying belt.
- An image forming apparatus incorporates the aforementioned developing apparatus.
- A developing apparatus includes a developer bearing body, a first shaft, a second shaft, a developer supplying belt, and a power supply. The developer bearing body is in contact with an image forming body. The first shaft is driven in rotation by an external drive source. The developer supplying belt is entrained about the first shaft and second shaft, the developer supplying belt being partially in a wrapping contact with the developer bearing body. The power supply applies voltages to the first shaft and the second shaft such that a voltage drop appears in the developer supplying belt in a direction of travel of the developer supplying belt. The power supply applies a voltage to the developer bearing body such that a first electric field having a first direction is developed across the developer bearing body and a first portion of the developer supplying belt in contact with the developer bearing body, and such that a second electric field having a second direction opposite to the first direction is developed across the developer bearing body and a second portion of the developer supplying belt in contact with the developer bearing body.
- The first electric field allows the developer to be supplied from the developer supplying belt to the developer bearing body.
- The second electric field allows the developer to be recovered from the developer bearing body to the developer supplying belt.
- The developing apparatus further includes an urging member that urges the developer supplying belt to maintain the developer supplying belt in tension.
- The developer supplying belt is formed of a semi-conductive material having a volume resistivity in the range of 106 to 108 Ωcm.
- The developing apparatus further includes a rotating body that rotates in contact with the developer supplying belt at a portion after the developer has been recovered from the developer bearing body to the developer supplying belt.
- Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
- The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limiting the present invention, and wherein:
-
FIGS. 1A and 1B illustrate a general configuration of a developing unit of an image forming apparatus of a first embodiment; -
FIG. 2 illustrates a general configuration of a print engine; -
FIGS. 3 and 4 illustrate the voltages appearing on points P1 and P2, respectively; -
FIG. 5 illustrates a pertinent portion of a printer of a second embodiment; and -
FIG. 6 illustrates the development process of a second embodiment. - The invention will be described in detail with reference to the accompanying drawings. The image apparatus according to the invention will be described with respect to a printer.
-
FIG. 1A illustrates a general configuration of a developing unit of an image forming apparatus. -
FIG. 2 illustrates a general configuration of a print engine. - Referring to
FIGS. 1A and 2 , aphotoconductive drum 11 includes an outer layer formed of an organic photoconductive material. A chargingroller 12 uniformly charges the surface of thephotoconductive drum 11 to approximately −600 V. The chargingroller 12 is in rolling contact with thephotoconductive drum 11, thereby minimizing wear of the surface of thephotoconductive drum 11 due to friction. A negative direct current voltage is applied across the chargingroller 12 and thephotoconductive drum 11. - An
LED print head 13 includes light emitting diodes (LEDs) as a light source, and illuminates the charged surface of thephotoconductive drum 11 to form an electrostatic latent image. A laser print head may be used in place of the LED print head. - A developing
unit 21 includes a developingroller 14, atoner supplying belt 16, a developingblade 20, and a toner reservoir 17. The developingroller 14supplies toner 18 to thephotoconductive drum 11. The developingblade 20 forms a thin layer oftoner 18 on the developingroller 14. The toner reservoir 17 holds thefresh toner 18 therein. - The developing
roller 14 is in contact with or in proximity to thephotoconductive drum 11. The developingroller 14 rotates in a direction shown by arrow B, opposite to the direction shown by arrow A in which thephotoconductive drum 11 rotates. The developingroller 14 supplies thetoner 18 to the electrostatic latent image on thephotoconductive drum 11, thereby developing the electrostatic latent image into a toner image. The toner image is transferred onto paper 29 with the aid of atransfer roller 15. Theresidual toner 18 remaining on thephotoconductive drum 11 after transfer is removed by acleaning blade 19 which serves as a cleaning device of the blade type. The paper 29 is then advanced to a fixing unit where the toner image is fused into the paper 29. - The developing
roller 14 includes a metal shaft and a resilient layer formed on the metal shaft. The resilient layer is formed of a material such as silicone rubber or urethane rubber having a volume resistivity in the range of 108 to 1010 Ωcm. A coating layer may be formed on the resilient layer. The developingroller 14 has a diameter of, for example, 20 mm. - The developing
blade 20 is formed of a thin metal plate having a bent end portion which is in pressure contact with the outer surface of the developingroller 14. Thetoner supplying belt 16 is formed of a material such as semi-conductive urethane resin, polyimide resin, polyimideamide resin, urethane rubber, CR rubber, or silicone rubber. Thetoner supplying belt 16 has a volume resistivity in the range of 106 to 108 Ωcm, and a surface roughness Rz in the range of 5 to 15 μm. - The
toner supplying belt 16 is entrained about adrive shaft 16 a and a drivenshaft 16 b, which are formed of a highly electrically conductive material such as metal. When thedrive shaft 16 a rotates, thetoner supplying belt 16 runs. As a result, the drivenshaft 16 b also rotates. The drivenshaft 16 b is urged bycoil springs 22 in a direction away from thedrive shaft 16 a, so that thetoner supplying belt 16 is maintained in a predetermined tension. - The
toner supplying belt 16 between thedrive shaft 16 a and drivenshaft 16 b partially wraps around the developingroller 14 such that thetoner supplying belt 16 is in contact with the developingroller 14 over a circumferential distance L of the developing roller greater than a nip formed between the developingroller 14 and a conventional toner supplying roller of sponge. For example, the conventional toner supplying roller having a diameter of 20 mm forms a nip of about 2 mm while thetoner supplying belt 16 wraps around the developingroller 14 over a circumferential distance L of about 10 mm, from point P1 to point P2. When thedrive shaft 16 a rotates, thetoner supplying belt 16 and the developingroller 14 run at substantially the same circumferential speed but in the opposite direction at the area in which the developingroller 14 rotates in contact with thetoner supplying belt 16. - The
toner 18 is one-component toner containing a resin such as polyester or polystyrene, a coloring agent, a releasing agent, and a charge control agent. An external additive such as silica is added to the surface of the toner. The toner is manufactured by pulverization or by polymerization. Thetoner 18 has a volume mean particle diameter in the range of 3-10 μm and an average degree of sphericity in the range of 0.9-0.98. - The average degree of sphericity of the
toner 18 is obtained by dividing the total number of degrees of sphericity of toner particles by the number of the toner particles (e.g., 3500). The average degree of sphericity is measured with a particle size and shape image analysis flow cytometer (MODEL FPIA-2000, available from Sysmex Corporation). Degree of sphericity is a measure of surface roughness of thetoner 18, and is given by the following equation. -
Degree of sphericity=(total length of the perimeter of a projected area of a particle)/(total length of the perimeter of a projected image of a particle) - The projected area of a particle is an area of the projection of a particle and is a binary image. The total length of the perimeter of a projected image of a particle is a sum of lengths between two adjacent edge points on the perimeter.
- If a toner particle is perfectly spherical, the degree of sphericity of the particle is 1.00. The degree of sphericity of a toner particle becomes smaller with increasing complexity of its shape.
- The amount of charge of the
toner 18 is measured by the charge blow-off method, and is in the range of −60 to −20 μQ/g depending on the charging agent and the external additive. Ahigh voltage supply 81 applies a voltage VD to the developingroller 14. Ahigh voltage supply 82 applies a voltage VL to the developingblade 20. Ahigh voltage supply 83 applies a voltage VS to thedrive shaft 16 a. Ahigh voltage supply 84 applies a voltage VR to the drivenshaft 16 b. - The operation of the printer of the aforementioned configuration will be described.
- When image formation is initiated, a drive motor (not shown) rotates to drive the
photoconductive drum 11, developingroller 14, and driveshaft 16 a in rotation in directions shown by arrows A, B, and D, respectively. Thetoner supplying belt 16 runs in the toner reservoir 17 with thetoner 18 adhering to the toner supplying belt 17. Thetoner 18 adheres to thetoner supplying belt 16 by Van der Waals force and very small Coulomb forces resulting from the surface roughness of thetoner supplying belt 16. As thetoner supplying belt 16 runs, thetoner 18 on thetoner supplying belt 16 is brought into contact with the developingroller 14 at point P1. -
FIGS. 3 and 4 illustrate the voltages appearing on points P1 and P2, respectively. - When the voltages VS and VR are applied to the
drive shaft 16 a and drivenshaft 16 b, respectively, the voltages at points P1 and P2 are given as follows: -
Vp1={Db/(Da+Db)}×(VS−VR) (1) -
Vp2={Df/(De+Df)}×(VS−VR) (2) - where Vp1 is a voltage at point P1, Vp2 is a voltage at point P2, Da is the distance between point P1 and the
drive shaft 16 a, Db is the distance between point P1 and the drivenshaft 16 b, De is the distance between the point P2 and thedrive shaft 16 a, and Df is a distance between the point P2 and the drivenshaft 16 b. - In other words, the voltage difference Vs−VR is apportioned by the resistances proportional to the distance Da and Db, resulting in voltage drops Vp1 and Vp2 at points P1 and P2, respectively.
- When the voltages VS, VR, and VD are −500 V, 0, and −250 V, and the distances Da and Db are 2 mm and 18 mm, respectively, the voltage at point P1 is −450 V from Equation (1). In other words, when the voltage VD is −250, Vp1 is −450, which creates an electric field required for the negatively charged toner 18 (e.g., −60 to −20 μQ/g) to be transferred onto the developing
roller 14. - When the
toner 18 deposited on the developingroller 14 passes under the developingblade 20, theblade 20 forms a thin layer oftoner 18. The voltage VL is applied to the developingroller 20 for controlling the amount of charge and the thickness of the toner layer formed on the developingroller 14. As the developingroller 14 rotates in contact with thephotoconductive drum 11, the thin layer oftoner 18 is brought into contact with the electrostatic latent image formed on thephotoconductive drum 11, thereby developing the electrostatic latent image with thetoner 18 into a toner image. - A portion of the thin layer that is not brought into contact with the electrostatic latent image remains on the developing
roller 14, and reaches point P2 as the developingroller 14 rotates further. - When the distances De and Df are 18 mm and 2 mm, respectively, a voltage of −50 V appears on point P2. In other words, when the voltage VD is −250 V, Vp2 is −50 V, which creates an electric field required for the negatively charged
toner 18 to be transferred onto thetoner supplying belt 16. - The
toner 18 deposited on thetoner supplying belt 16 reaches point P1 as thetoner supplying belt 16 runs. - As described above, the voltage Vp1 at point P1 at which the
toner supplying belt 16 moves into contact with the developingroller 14 differs from the voltage at point P2 at which thetoner supplying belt 16 moves out of contact with the developingroller 14. The voltage Vp1 serves to establish an electric field through which thetoner 18 is supplied from thetoner supplying belt 16 to the developingroller 14. The voltage Vp2 serves to establish an electric field through which the remainingtoner 18 is recovered from the developingroller 14 to thetoner supplying belt 16. - Thus, the
toner 18 remaining on the developing roller after the development of an electrostatic latent image may be removed from the developingroller 14. This eliminates the chance of thetoner 18 remaining on the developingroller 14 of being reused in the subsequent development cycle, thereby preventing the remainingtoner 18 from forming a reverse image of the electrostatic latent image as a whole. - The
toner 18 recovered by thetoner supplying belt 16 is then delivered to point P1, being re-used efficiently. - Because a conventional
toner supplying roller 16 is formed of sponge, thetoner supplying roller 16 will deteriorate after a relatively short-time use, causing variations of supply of thetoner 18 to the developingroller 14 even within a page of image, resulting in variations in the density of image. - The pressure applied by the
toner supplying belt 16 against the developingroller 14 may be controlled by adjusting the urging force of the coil springs 22 such that thetoner supplying belt 16 exerts a relatively small abutting force on the developingroller 14. A small abutting force not only prolongs the useful life of thetoner supplying belt 16 but also minimizes the force that rubs the surface of the developingroller 14, preventing the quality oftoner 18 from being deteriorated as well as ensuring reliable image quality. The abutting force is preferably in the range of 5 to 20 g/cm for reliable abutment of thetoner supplying belt 16 against the developingroller 14. -
FIG. 1B illustrates a general configuration of a developing unit of an image forming apparatus where thetoner supplying belt 16 is not in contact with the developingroller 14 but in proximity to the developingroller 14. Just as in the case ofFIG. 1A , thehigh voltage supply 81 applies the voltage VD to the developingroller 14. Thehigh voltage supply 83 applies the voltage VS to thedrive shaft 16 a. Thehigh voltage supply 84 applies the voltage VR to the drivenshaft 16 b. In a similar manner to the voltages Vp1 and Vp2 given by Equations (1) and (2) , the voltage Vp4 and the voltage Vp5 appears at point P4 and point P5, respectively. The voltage Vp4 creates an electric field across the developingroller 14 and thetoner supplying belt 16 in a direction such that the chargedtoner 18 may be transferred from thetoner supplying belt 16 to the developingroller 14. The voltage Vp5 creates an electric field across the developingroller 14 and thetoner supplying roller 16 in a direction such that the chargedtoner 18 may be transferred from the developingroller 14 to thetoner supplying belt 16. Thus, the configuration inFIG. 1B also provides the same advantages as that shown inFIG. 1A . - Elements similar to those in the first embodiment have been given the same reference numerals and the description thereof is omitted.
-
FIG. 5 illustrates a pertinent portion of a printer of the second embodiment. -
FIG. 6 illustrates the development process of a second embodiment. - Referring to
FIG. 5 , a developingunit 24 includes atoner delivering roller 23 that rotates. Thetoner delivering roller 23 includes an electrically conductive shaft formed of a metal material. The electrically conductive shaft is covered with a semi-conductive rubber material or a foamed rubber material. The semi-conductive rubber material may be urethane or silicone and have a volume resistivity in the range of 106-108 Ωcm. The foamed rubber material may be urethane or silicone and have a volume resistivity in the range of 106-108 Ωcm. When image formation is initiated, a drive motor (not shown) rotates to drive aphotoconductive drum 11, a developingroller 14,toner delivering roller 23, and adrive shaft 16 a in rotation in directions shown by arrows A, B, and D, respectively. - The
toner delivering roller 23 parallels to a developingroller 14 and is on the side of atoner supplying belt 16 opposite thetoner developing roller 14. Thetoner delivering roller 23 abuts thetoner supplying belt 16 between adrive shaft 16 a and drivenroller 16 b. Thetoner delivering roller 23 is driven by a drive motor (not shown) to rotate in a direction shown by arrow E, which is the same direction as thetoner supplying belt 16. Thetoner delivering roller 23 is in contact with thetoner supplying belt 16 at point P3. Thetoner delivering roller 23 and thetoner supplying belt 16 run in opposite directions at point P3. Thetoner delivering roller 23 is positioned relative to thetoner supplying belt 16 such that thetoner delivering roller 23 and thetoner supplying belt 16 make no wrapped portion or little or no nip. - A
power supply 85 applies a voltage VP to thetoner delivering roller 23. While thephotoconductive drum 11, developingroller 14,toner delivering roller 23, and adrive shaft 16 a have been described as being driven by the same motor (not shown), thetoner delivering roller 23 may be driven by a separate motor. - When the voltage VS is applied to the
drive shaft 16 a and the voltage VR is applied to the drivenshaft 16 b, the voltage at point P3 is given as follows: -
Vp3={Dh/(Dg+Dh)}×(VS−VR) (3) - where Vp3 is a voltage at point P3, Dg is the distance between point P3 and the
drive shaft 16 a, and Dh is the distance between point P3 and the drivenshaft 16 b. - In other words, the voltage difference VS−VR is apportioned by the resistances proportional to the distance Dg and Dh, resulting in the voltage Vp3 at point P3. The voltage Vp3 is substantially equal to the voltage VP.
- For example, when the voltages VS, VR, and VP are −500 V, 0 V, and −250 V, respectively, and the distances Dg and Dh are 10 mm, Vp3 is −250 V.
- The operation of a developing
unit 21 of the aforementioned configuration will be described. - Upon initiation of image formation, the drive motor is energized to drive the
photoconductive drum 11, developingroller 14,drive shaft 16 a, andtoner delivering roller 23 to rotate in directions shown by arrows A, B, D, and E. Thetoner delivering roller 23 rotates with thetoner 18 adhering thereto while thetoner supplying belt 16 runs with thetoner 18 adhering thereto. - The
toner 18 adhering to thetoner delivering roller 23 is brought into contact with thetoner supplying belt 16 at point P3. Because the voltage Vp3 at point P3 is substantially equal to the voltage VP applied to thetoner delivering roller 23, no significant electric field is developed betweentoner supplying belt 16 and thetoner delivering roller 23. Therefore, thetoner 18 is smoothly supplied from thetoner delivering roller 23 to thetoner supplying belt 16. The resultant thickness of toner layer on thetoner supplying belt 16 is substantially the same as that on thetoner delivering roller 23. - A portion of the thin layer that is not brought into contact with the electrostatic latent image remains on the developing roller, and reaches point P3 as the
toner supplying belt 16 runs further. Because of negligible electric field betweentoner supplying belt 16 and thetoner delivering roller 23, thetoner delivering roller 23 rubs thetoner 18 on thetoner supplying belt 16 to prevent the remainingtoner 18 from forming a reverse image of the electrostatic latent image as a whole. - Because the
toner delivering roller 23 delivers thetoner 18 to thetoner supplying belt 16 continuously, a layer of thetoner 18 may be formed on thetoner supplying belt 16. This ensures reliable supply of thetoner 18 to the developingroller 14. - The
toner 18 not used for the development of an electrostatic latent image is recovered by thetoner supplying belt 16, and the layer of thetoner 18 is scraped off thetoner supplying belt 16 by thetoner delivering roller 23. This provides reliable removal of the reversal image of the electrostatic latent image remaining in the layer of thetoner 18 formed on the developingroller 14. - Although the first and second embodiments have been described with respect to a printer, the present invention may be applicable to a copying machine, a facsimile machine, and a multi function apparatus of these machines.
- The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art intended to be included within the scope of the following claims.
Claims (18)
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JP2006-148403 | 2006-05-29 | ||
JP2006148403A JP4336353B2 (en) | 2006-05-29 | 2006-05-29 | Developing device and image forming apparatus |
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US20070274744A1 true US20070274744A1 (en) | 2007-11-29 |
US8023865B2 US8023865B2 (en) | 2011-09-20 |
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US11/753,596 Expired - Fee Related US8023865B2 (en) | 2006-05-29 | 2007-05-25 | Developing apparatus and image forming apparatus |
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Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20090202278A1 (en) * | 2008-02-12 | 2009-08-13 | Oki Data Corporation | Image forming apparatus |
US20110236079A1 (en) * | 2010-03-25 | 2011-09-29 | Canon Kabushiki Kaisha | Developing device and process cartridge |
US20210284428A1 (en) * | 2018-02-09 | 2021-09-16 | Sonoco Development, Inc. | Twist action portion control sauce dispenser |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
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JP5145910B2 (en) | 2007-12-07 | 2013-02-20 | 富士通株式会社 | Information processing apparatus and information processing method |
JP5280815B2 (en) * | 2008-11-27 | 2013-09-04 | 株式会社沖データ | Developing device and image forming apparatus |
JP4875121B2 (en) | 2009-06-26 | 2012-02-15 | 株式会社沖データ | Developing device and image forming apparatus |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
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JPS61292180A (en) * | 1985-06-19 | 1986-12-22 | Matsushita Graphic Commun Syst Inc | Electrophotograph recording device |
JPH0746246B2 (en) | 1985-10-23 | 1995-05-17 | 株式会社リコー | Development device |
JP3484814B2 (en) | 1995-04-20 | 2004-01-06 | セイコーエプソン株式会社 | Developing device |
JP2003043818A (en) | 2001-07-31 | 2003-02-14 | Canon Inc | Developing device |
JP2003131490A (en) * | 2001-10-30 | 2003-05-09 | Canon Inc | Developer carrying means, developing device and image forming device |
JP2006106223A (en) | 2004-10-01 | 2006-04-20 | Konica Minolta Business Technologies Inc | Supply/collection apparatus and image forming apparatus |
-
2006
- 2006-05-29 JP JP2006148403A patent/JP4336353B2/en not_active Expired - Fee Related
-
2007
- 2007-05-25 US US11/753,596 patent/US8023865B2/en not_active Expired - Fee Related
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20090202278A1 (en) * | 2008-02-12 | 2009-08-13 | Oki Data Corporation | Image forming apparatus |
US8200132B2 (en) * | 2008-02-12 | 2012-06-12 | Oki Data Corporation | Image forming apparatus |
US20110236079A1 (en) * | 2010-03-25 | 2011-09-29 | Canon Kabushiki Kaisha | Developing device and process cartridge |
US8548363B2 (en) * | 2010-03-25 | 2013-10-01 | Canon Kabushiki Kaisha | Developing device and process cartridge |
US20210284428A1 (en) * | 2018-02-09 | 2021-09-16 | Sonoco Development, Inc. | Twist action portion control sauce dispenser |
US11505396B2 (en) * | 2018-02-09 | 2022-11-22 | Sonoco Development, Inc. | Twist action portion control sauce dispenser |
Also Published As
Publication number | Publication date |
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JP4336353B2 (en) | 2009-09-30 |
JP2007316532A (en) | 2007-12-06 |
US8023865B2 (en) | 2011-09-20 |
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